Dwarf Fortress Bug Tracker - Dwarf Fortress
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0001791Dwarf FortressMap Featurespublic2010-05-06 18:392015-12-04 21:51
normalmajorhave not tried
0001791: Magma sea breaching into Hell
Sometimes in the divisions between the local map quad's there's such a steep cliff that the hell layer moves so upwards it breaches the magma sea from the side. Obvious effects include lag due to absurd flow simulation, magma pipes drying out and demonic invasion.

Here are two threads on the forums relating the same bug:

(Hence why I put the "unknown" tag on the platform/OS. I don't know what those people used)

http://www.bay12forums.com/smf/index.php?topic=56244 [^]
http://www.bay12forums.com/smf/index.php?topic=56707.0 [^]

Given how obscene cliff sites are popular as fort locations, this bug jeopardizes many fortress construction efforts.
Embark on a site with very very very extreme cliffs.
Dig down to hell or reveal the map.
My own theory about this :P

This happened because DF generetes the terrain on each one of its 48x48 quads more or less independently, and each of the 48x48 quads seems to have some "height" measure of its own.
Whenever you are in a map with global worldgen terrain "steps" like this one, the quad's internal height values don't match properly, and you have those maps where there are one or two Z-levels of discrepancy between the magma sea on the "high" and "low" tiles (specially common on mountainsides). However since the magma sea is thick, and so is the SMR layer below it, we don't have many issues (other than the odd dwarf digging into the magma sea from the SIDE, yes it can happen).
In this case because the fort sits on an obscene cliff, the "fault" between the quads is so great that the magma sea's side breached into hell, and voila, you have this.. There's a perfect match between where the giant cliff starts and where the magma sea breaches into hell.

Some screenshots in stonesense (save is also available somewhere in that thread)

http://www.bay12forums.com/smf/index.php?topic=56244.msg1223809#msg1223809 [^]
No tags attached.
related to 0000051resolved Footkerchief Cavern collapse at embark 
related to 0003310resolved Footkerchief areas of semimolten rock and magma sea intersect with higher geological features in a very rectilinear manner. 
related to 0000127new  Muddy open space in magma pipe 
parent of 0002411resolved Footkerchief Volcano that pierces water cavern layer will drain into magma sea plus cave-ins. 
related to 0008190new  Embark Location has 2000+ Z Levels. Crashes on initial unpause 
Issue History
2010-05-06 18:39KefkaNew Issue
2010-05-06 18:41FootkerchiefRelationship addedrelated to 0000098
2010-05-06 18:41FootkerchiefCategoryGeology => Map Features
2010-05-07 06:49SkandrakenIssue Monitored: Skandraken
2010-05-13 05:50Urist ImiknorrisNote Added: 0006636
2010-07-14 11:35FootkerchiefRelationship addedrelated to 0000051
2010-07-14 11:35FootkerchiefRelationship deletedrelated to 0000098
2010-07-14 11:39FootkerchiefRelationship addedparent of 0002411
2010-10-31 18:37KarlitoNote Added: 0013573
2010-12-05 15:41FootkerchiefRelationship addedrelated to 0002713
2010-12-12 00:14VideospiritNote Added: 0014549
2010-12-12 02:07Hieronymous AlloyIssue Monitored: Hieronymous Alloy
2011-03-27 09:08csebalNote Added: 0016674
2011-03-27 09:09csebalNote Edited: 0016674bug_revision_view_page.php?bugnote_id=0016674#r6207
2011-03-27 09:10csebalNote Edited: 0016674bug_revision_view_page.php?bugnote_id=0016674#r6208
2011-03-27 09:18csebalNote Edited: 0016674bug_revision_view_page.php?bugnote_id=0016674#r6209
2012-03-06 08:58FootkerchiefNote Added: 0021172
2012-03-06 08:58FootkerchiefRelationship addedrelated to 0003310
2012-03-06 08:59FootkerchiefRelationship deletedrelated to 0002713
2012-03-06 08:59FootkerchiefRelationship addedrelated to 0000127
2012-03-06 10:35Granite26Note Added: 0021178
2012-03-07 20:27DwarfuSticky IssueNo => Yes
2014-08-31 09:53lethosorRelationship addedrelated to 0008190
2015-12-02 01:23romeofallingNote Added: 0033248
2015-12-02 11:04jwoodward48dfNote Added: 0033282
2015-12-04 21:51ysuaIssue Monitored: ysua
2018-04-16 16:57HuntthetrollIssue Monitored: Huntthetroll

Urist Imiknorris   
2010-05-13 05:50   
It's official. This is the best bug this game has ever had.
2010-10-31 18:37   
I believe I have another instance of this bug. Tapped into the magma sea at a weird place and unleashed a hoard of demons. However, they don't appear to be able to path through the magma to reach my fortress.
http://dffd.wimbli.com/file.php?id=3348 [^]
2010-12-12 00:14   
Sometimes a Deep pit or a cave will do this too. Had this problem on my current civs won't pickup non military equipment bug fort. Used DFhack dfliquids to seal the leaks and boosted my fps a little, although not as much as I'd hoped.
2011-03-27 09:08   
(edited on: 2011-03-27 09:18)
Actually, i managed to gen a map, where hell not only reaches the magma sea, but goes straight through it on two grid cells, almost reaching the cavern layer below.

Normal hell starts at Z-68, except for two cells, that start at Z-45. Suffice to say, i was able to dig straight down into it without going past any obstacles.

The two adjacent cells in question are situated under a 'peak' of sorts, so the relative difference in height between hell and the surface is about the same as for the rest of the map, except that in this case, that relative difference places things a bit higher than usual.

Also besides the two cells mentioned above, there are 5 others that behave the opposite way. In them, the rock layers go deeper than they should, skipping both the magma sea and the slade layers and ending straight in hell.

http://tinypic.com/r/fz6tg0/7 [^]

image of Z-67. Z-68 is universally hell in all grid cells. the two hell cells on the right stretch up to Z-45.

The embark area has some 10+ 20+ cliffs, thanks to a volcano.

http://dffd.wimbli.com/file.php?id=4052 [^]

2012-03-06 08:58   
The OP's original save did not appear to exhibit save corruption.
2012-03-06 10:35   
This should be easier to replicate at will be lowering the number of layers. In theory, it should be possible to have hell breach the surface by removing all cavern layers and then embarking on an extreme cliff.
2015-12-02 01:23   
I believe I also have this bug. My entire map dropped two z levels and crashed onto whatever was below.

I located a backup and replayed, but the bug did not duplicate, so I am not including a save file on DFFD.
2015-12-02 11:04   
That may not be the same bug. The "entire map" should never crash, as it is supported from the side. Therefore, no amount of cliffs should cause a cavein.